The Origin of Anomalous Thermal Expansion Behavior in Calcium- Silicate-Hydrates

Author(s): N M Anoop Krishnan, Bu Wang, Gabriel Falzone, Yann Le Pape, Narayanan Neithalath, Laurent Pilon, Mathieu Bauchy and Gaurav Sant
Paper category: Proceedings
Book title: Proceeding of the 71st RILEM Annual Week & ICACMS 2017
Editor(s): Manu Santhanam, Ravindra Gettu, Radhakrishna G. Pillai, Sunitha K. Nayar
ISBN:978-2-35158-195-7, 978-2-35158-190-2 (Set)
e-ISBN: 978-2-35158-191-9
Publisher: RILEM Publications SARL
Publication year: 2017
Pages: 353-360
Total Pages: 8
Language : English

Abstract: Upon a change in their temperature, materials experience volume changes whose magnitude, and sign is described by their thermal deformation coefficient (TDC, also known as the coefficient of thermal expansion, CTE). Understanding, and predicting the TDC is of critical importance for structural materials, e.g., glass, structural ceramics or concrete, as uncontrolled changes in their volume can result in stress development, and thermal cracking. Using atomistic simulations, we investigate the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H) – the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behaviour arises from an increase in the degree of confinement of water contained in the C-S- H’s structure. We show that, in turn, this increase in confinement is controlled by the topology of the C-S-H’s atomic network. Taken together, the results suggest that thermal deformations of C-S-H depend not only on the composition, but also on the topology of substrate network. Thus, the study provides insights into potential techniques to mitigate thermal cracking in cement through a topological optimization of the layered silicate network.

Online publication :2017
Publication type :full_text
Public price (Euros) : 0.00